(a)
The recurrence, or a tendency to a recurrence, of the original type of a species in the progeny of its varieties; resemblance to remote rather than to near ancestors; reversion to the original form.
(b)
(Biol.) The recurrence of any peculiarity or disease of an ancestor in a subsequent generation, after an intermission for a generation or two. "Now and then there occur cases of what physiologists call atavism, or reversion to an ancestral type of character."
